Staples for generating and applying compression within a body

ABSTRACT

A staple comprising: a bridge configured to be elastically stretchable; a first leg connected to said bridge and configured to be elastically bendable; and a second leg connected to said bridge and configured to be elastically bendable; said first and second legs being connected to said bridge so that they are angled toward one another when they are in an unstrained state; such that when said bridge is elastically strained into an elongated condition, and said first and second legs are elastically strained so that they extend substantially parallel to one another, and said first and second legs are disposed in appropriate holes on opposing sides of a fracture line, and when the strain on said staple is thereafter released, compression will be provided across the fracture line by both said bridge and said first and second legs.

REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. application Ser. No.15/684,183 filed on Aug. 23, 2017, which is a continuation of U.S.patent application Ser. No. 14/540,351 filed on Nov. 13, 2014, now U.S.Pat. No. 9,855,036 issued on Jan. 2, 2018, which claims benefit of U.S.Provisional Patent Application Ser. No. 61/903,820, filed Nov. 13, 2013,which patent application is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to staples for generating, applying, andmaintaining compression to a site in a human or animal body in order tofacilitate healing of diseased or damaged tissue. The invention findsparticular utility in the field of orthopedics and specifically forreducing fractures and maintaining compression between bone fragments.While the invention has application throughout the body, its utilitywill be illustrated herein in the context of the repair of fractured ordisplaced bone tissue, such as during an Akin Osteotomy of the foot oran Isolated Lunocapitate Arthrodesis of the hand/wrist.

BACKGROUND OF THE INVENTION

In the field of orthopedic surgery it is common to rejoin broken bones.The success of the surgical procedure often depends on the ability toreaproximate the fractured bones, the amount of compression achievedbetween the bone fragments, and the ability to sustain that compressionover a period of time. If the surgeon is unable to bring the bonefragments into close contact, a gap will exist between the bonefragments and the bone tissue will need to fill that gap before completehealing can take place. Furthermore, gaps between bone fragments thatare too large allow motion to occur between the bone fragments,disrupting the healing tissue and thus slowing the healing process.Optimal healing requires that the bone fragments be in close contactwith each other, and for a compressive load to be applied and maintainedbetween the bone fragments. Compressive strain between bone fragmentshas been found to accelerate the healing process in accordance withWolf's Law.

Broken bones can be rejoined using staples. Staples are formed from aplurality of legs (typically two legs, though sometimes more) connectedtogether by a bridge. Staples are typically manufactured from eitherstainless steel alloys, titanium alloys or Nitinol, a shape memoryalloy. The staples are inserted into pre-drilled holes on either side ofthe fracture site.

While these staples are designed to bring the bone fragments into closecontact and to generate a compressive load between the bone fragments,the staples do not always succeed in accomplishing this objective. It iswidely reported that the compressive load of staples dissipates rapidlyas the bone relaxes and remodels around the legs of the staples.

Thus there exists a clinical need for fixation devices that are able tobring bone fragments into close proximity with each other, generate acompressive load, and maintain that compressive load for a prolongedperiod of time while healing occurs.

Moreover, existing staples have bridges that are fixed in size, shape,and dimension, while each procedure presents a unique anatomicalrequirement (which is set by a combination of indication andpatient-specific anatomy). Existing staples with fixed shape anddimension bridges will often sit “proud” of the cortical bone, resultingin irritated and inflamed adjacent soft tissue and, in some cases,bursitis.

Thus there also exists a clinical need for a staple with a malleablebridge that may be bent so as to conform to the unique anatomicalstructure of each patient and sit flush on the cortical surface of thebone.

SUMMARY OF THE INVENTION

The present invention provides a novel fixation device which is able tobring bone fragments into close proximity with each other, generate acompressive load, and maintain that compressive load for a prolongedperiod of time while healing occurs.

Among other things, the present invention comprises the provision anduse of a novel monolithic staple which is manufactured from a singlepiece of shape memory material (e.g., a material capable of exhibitingsuperelasticity and/or a temperature-induced shape change). The shapememory material may be a metal alloy (e.g., Nitinol) or a polymer (e.g.,appropriately processed PEEK). The staple is designed to reducefractures and generate and maintain more uniform compression between thecortical bone and cancellous bone of the bone fragments to aid infracture healing.

In one form of the invention, the staple comprises an elastic bridge andtwo elastic legs. The bridge and the legs meet at a pair of curved hingeregions which are also elastic. In the un-restrained state, the legs ofthe staple are bent inward with an angle of less than 90°. Prior toimplantation, the bridge of the staple can be reversibly strainedoutward (i.e., stretched longitudinally outward) and the legs of thestaple can be reversibly bent to a position perpendicular to thelongitudinal axis of the bridge so as to allow for insertion of thestaple into a prepared fracture site. A delivery device may be used tostrain the bridge, bend the legs to parallel, hold the staple in thisstrained state prior to implantation, and insert the strained stapleinto the prepared fracture site. The constraint on the bridge and legsis removed, whereupon the bridge and legs attempt to return to theiroriginal unrestrained state, thereby generating a greater, and moreuniform, compressive load and maintaining that greater, and moreuniform, compressive load for a prolonged period of time while healingoccurs.

In another form of the invention, the staple comprises a malleablebridge and two elastic legs. The bridge and the legs meet at a pair ofcurved hinge regions which are also elastic. In the unrestrained state,the legs of the staple are bent inward with an angle of less than 90°.Prior to implantation, the malleable bridge may be deformed so that itconforms to the unique anatomical structure of the patient, such that itwill sit flush with the cortical surface of the bone after implantation.And prior to implantation, the legs of the staple can be reversibly bentto a position perpendicular to the longitudinal axis of the bridge so asto allow for insertion of the staple into a prepared fracture site. Abending device may be used to deform the bridge, and a delivery devicemay be used to hold the deformed bridge, bend the legs, hold the staplein this state prior to implantation, and insert the staple into thebone, with the bridge of the staple extending across the fracture line.Alternatively, a combined bending/delivery device may be used to deformthe bridge, bend the legs, hold the staple in this condition prior toimplantation, and insert the staple into the bone, with the bridge ofthe staple extending across the fracture line. Upon insertion of thedeformed and strained staple into the prepared fracture site, theconstraint on the legs of the staple is removed, whereupon the legs ofthe staple attempt to return to their original unrestrained state,thereby generating a compressive load and maintaining that compressiveload for a prolonged period of time while healing occurs. Significantly,the deformed bridge of the staple can be matched to the uniqueanatomical structure of the patient, such that the bridge of the staplewill sit flush with the cortical surface of the bone.

Additionally, it is possible that where the staple comprises a malleablebridge with two elastic legs, the staple can be inserted into thefracture site prior to bending the bridge. The bridge can be bent afterimplantation using a tamp-like device of the sort known in the art.

In one preferred form of the invention, there is provided a staplecomprising:

-   -   a bridge configured to be elastically stretchable;    -   a first leg connected to said bridge and configured to be        elastically bendable; and    -   a second leg connected to said bridge and configured to be        elastically bendable;    -   said first and second legs being connected to said bridge so        that they are angled toward one another when they are in an        unstrained state;    -   such that when said bridge is elastically strained into an        elongated condition, and said first and second legs are        elastically strained so that they extend substantially parallel        to one another, and said first and second legs are disposed in        appropriate holes on opposing sides of a fracture line, and when        the strain on said staple is thereafter released, compression        will be provided across the fracture line by both said bridge        and said first and second legs.

In another preferred form of the invention, there is provided a methodfor providing compression across a fracture line, the method comprising:

-   -   providing a staple comprising:        -   a bridge configured to be elastically stretchable;        -   a first leg connected to said bridge and configured to be            elastically bendable; and        -   a second leg connected to said bridge and configured to be            elastically bendable;        -   said first and second legs being connected to said bridge so            that they are angled toward one another when they are in an            unstrained state;    -   elastically straining said bridge into an elongated condition,        and elastically straining said first and second legs so that        they extend substantially parallel to one another;    -   inserting said first and second legs in appropriate holes on        opposing sides of a fracture line; and    -   releasing the strain on said staple so that compression is        provided across the fracture line by both said bridge and said        first and second legs.

In another preferred form of the invention, there is provided a staplecomprising:

-   -   a malleable bridge configured to be inelastically deformed;    -   a first leg connected to said bridge and configured to be        elastically bendable; and    -   a second leg connected to said bridge and configured to be        elastically bendable;    -   said first and second legs being connected to said bridge so        that they are angled toward one another when they are in an        unstrained state;    -   such that when said bridge is inelastically deformed, and said        first and second legs are elastically strained so that they        extend substantially parallel to one another, and said first and        second legs are disposed in appropriate holes on opposing sides        of a fracture line, and when the strain on said staple is        thereafter released, compression will be provided across the        fracture line by said first and second legs.

In another preferred form of the invention, there is provided a methodfor providing compression across a fracture line, the method comprising:

-   -   providing a staple comprising:        -   a malleable bridge configured to be inelastically deformed;        -   a first leg connected to said bridge and configured to be            elastically bendable; and        -   a second leg connected to said bridge and configured to be            elastically bendable;        -   said first and second legs being connected to said bridge so            that they are angled toward one another when they are in an            unstrained state;    -   inelastically deforming said bridge, and elastically straining        said first and second legs so that they extend substantially        parallel to one another;    -   inserting said first and second legs in appropriate holes on        opposing sides of a fracture line; and    -   releasing the strain on said staple so that compression is        provided across the fracture line by said first and second legs.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which is tobe considered together with the accompanying drawings wherein likenumbers refer to like parts, and further wherein:

FIG. 1 is a schematic view of a novel staple formed in accordance withthe present invention, wherein the staple comprises a bridge which iscapable of being elastically strained and legs which are capable ofbeing elastically strained, and further wherein the staple is shown inits unstrained condition;

FIG. 2 is a schematic view of the novel staple shown in FIG. 1, whereinthe bridge of the staple has been elastically strained (i.e.,longitudinally stretched) and the legs of the staple have beenelastically bent outwards;

FIG. 3 is a schematic view showing how the elastically strained stapleof FIG. 2 will foreshorten along its bridge, and have its legs “kickinward”, when the strain on the staple is removed;

FIGS. 4 and 5 are schematic views showing an exemplary delivery devicewhich may be used with the novel staple shown in FIG. 1 to elasticallystrain (i.e., stretch) the bridge of the staple and elastically bend thelegs of the staple;

FIGS. 6 and 7 are schematic views showing the delivery device of FIGS. 4and 5 being used with the novel staple shown in FIG. 1 to elasticallystrain (i.e., stretch) the bridge of the staple and elastically bend thelegs of the staple;

FIG. 8 is a schematic view showing how the novel staple of FIG. 1 may beused to generate and maintain a greater, and more uniform, compressionbetween bone fragments so as to aid in fracture healing;

FIGS. 8A, 8B and 8C are schematic views showing another form of deliverydevice which may be used with the novel staple shown in FIG. 1 toelastically strain (i.e., stretch) the bridge of the staple andelastically bend the legs of the staple;

FIGS. 9 and 10 are schematic views of another novel staple formed inaccordance with the present invention, wherein the staple comprises amalleable bridge which is capable of being inelastically deformed andlegs which are capable of being elastically strained, and furtherwherein FIG. 9 shows the staple in its unstrained condition and FIG. 10shows the staple with its bridge bent but its legs in an unstrainedcondition;

FIG. 10A is a schematic view of another novel staple formed inaccordance with the present invention, wherein the staple has a bridgethat is convex;

FIGS. 11 and 12 are schematic views showing an exemplary bending devicewhich may be used with the novel staple shown in FIGS. 9 and 10 toinelastically bend the bridge of the staple to more appropriatelyconform to the surface profile of the cortical bone;

FIG. 13 is a schematic view which shows the staple of FIGS. 9 and 10after the bridge of the staple has been inelastically bent and after thelegs of the staple have been elastically strained into a parallelcondition;

FIGS. 14-16 are schematic views showing a plier assembly which may beused with the novel staple shown in FIGS. 9 and 10 to elastically strain(i.e., stretch) the legs of the staple after the bridge of the staplehas already been inelastically bent;

FIGS. 17 and 18 are schematic views showing how the novel staple shownin FIGS. 9 and 10 may have the bridge of the staple inelastically bentto conform to the surface profile of a bone, the legs of the stapleelastically bent into a parallel condition, and the staple thereafterdeployed in bone so as to provide compression across a fracture.

FIG. 19 is a schematic view of another novel staple formed in accordancewith the present invention, wherein the staple comprises a malleablebridge which is capable of being inelastically deformed and legs whichare capable of being elastically strained, and further wherein thebridge of the staple has been deformed to have a convex configurationafter bending; and

FIGS. 20 and 21 are schematic views of another novel device which may beused to bend the bridge of the staple shown in FIG. 10A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Novel StapleComprising Elastic Bridge with Two Elastic Legs

Looking first at FIG. 1, there is shown a novel staple 5 which is ableto bring bone fragments into close proximity with each other, generate agreater, and more uniform (i.e., across the cortical bone and thecancellous bone), compressive load across the fracture line, andmaintain that greater, and more uniform, compressive load for aprolonged period of time while healing occurs.

Novel staple 5 is preferably an integral, monolithic structuremanufactured from a single piece of shape memory material (e.g., amaterial capable of exhibiting superelasticity and/or atemperature-induced shape change). The shape memory material may be ametal alloy (e.g., Nitinol) or a polymer (e.g., appropriately processedPEEK). Staple 5 is designed to reduce fractures and generate andmaintain greater, and more uniform, compression between bone fragmentsto aid in fracture healing. Staple 5 comprises an elastic bridge 10 andtwo elastic legs 15. Bridge 10 and legs 15 meet at a pair of curvedhinge regions 20 which are also elastic. Legs 15 may have barbed teeth25 to help the legs of the staple grip into the bone after implantation(see below) and prevent the legs of the staple from working their wayback out of the bone. In the un-restrained state, legs 15 of staple 5are bent inward with an angle of less than 90°. By way of example butnot limitation, in one preferred form of the invention, legs 15 extendat an angle of about 45° to the longitudinal axis of bridge 10 when intheir unrestrained state.

Prior to implantation, bridge 10 of staple 5 can be reversibly strainedoutward (i.e., stretched longitudinally) and legs 15 of staple 5 can bereversibly bent to a position substantially perpendicular to bridge 10(FIG. 2) so as to allow for insertion of the legs of the staple into aprepared fracture site, with the stretched bridge of the staple spanningacross the fracture line (see below). Note that where staple 5 is formedout of Nitinol, elastic deformations of up to approximately 8% areachievable. A delivery device (see below) can be used to strain bridge10 and to bend legs 15, hold the staple in this strained state prior toimplantation, and then insert the staple into the prepared fracturesite.

Upon insertion of the strained staple 5 into the prepared fracture site,the constraint on bridge 10 and legs 15 is removed, whereupon staple 5attempts to return to its original un-restrained state (FIG. 3), therebygenerating a greater compressive load with more uniformity along thefracture line (i.e., through legs 15 and compressive bridge 10), andmaintaining that compressive load for a prolonged period of time whilehealing occurs.

Looking next at FIGS. 4-7, there is shown an exemplary delivery device30 which may be used to strain (i.e., stretch) bridge 10 and bend legs15 of staple 5. Delivery device 30 comprises two arms 35 which arepivotally connected together at a pivot pin 40, whereby to provide apair of handles 45 on one end for actuating the delivery device, and astaple mount 50 on the other end for holding and straining staple 5.When staple 5 is mounted to staple mount 50 of delivery device 30 andhandles 45 are thereafter moved toward one another, staple mount 50translates apart, thus stretching bridge 10 of staple 5, and alsobending legs 15 of staple 5 outward to a position substantiallyperpendicular to the longitudinal axis of bridge 10. Delivery device 30preferably includes a locking feature 55 that facilitates holding staple5 in its strained state and allows for easy insertion of staple 5 into aprepared fracture site (see below) Note that locking feature 55 ispreferably configured so that the surgeon can strain the staple todifferent degrees, thereby (i) enabling the surgeon to tailor thecompressive force (e.g., by bending only legs 15, or by bending legs 15and straining bridge 10), and (ii) enabling the surgeon to tailor theamount of recoverable strain established across the fracture line (e.g.,by varying the amount that bridge 10 is stretched), depending on bonequality.

FIG. 5 shows a close-up of staple mount 50 of delivery device 30. Staplemount 50 comprises a channel 60 that receives bridge 10 of staple 5, andtwo staple-stretching linkages 65 which sit distal to, and help define,channel 60. The radii 67 of staple-stretching linkages 65 mate with thecurved hinge regions 20 of staple 5 when the legs 15 of the staple havebeen strained (i.e., bent) outward to a position substantiallyperpendicular to the longitudinal axis of bridge 10. Eachstaple-stretching linkage 65 is connected to the arms 35 by a pin 70.Pins 70 slide in a channels 75 provided on the staple-stretchinglinkages 65 (i.e., a first pin 70 mounted to a first staple-stretchinglinkage 65 slides in a channel 75 of the second staple-stretchinglinkage 65, and a second pin 70 mounted to the second staple-stretchinglinkage 65 slides in the channel 75 of the first staple-stretchinglinkage 65). Channels 75 are sized to limit the maximum amount of strainwhich may be imposed on bridge 10 of staple 5 by delivery device 30(i.e., channels 75 limit the extent to which bridge 10 of staple 5 maybe stretched).

FIGS. 6 and 7 show staple 5 being loaded onto delivery device 30 andstaple 5 being strained, i.e., bridge 10 being stretched and legs 15being bent so that they are perpendicular to the longitudinal axis ofbridge 10. More particularly, FIG. 6 shows staple 5 loaded onto staplemount 50 of delivery device 30 while staple mount 50 of delivery device30 is in its closed (i.e., non-staple-straining) position. This is doneby positioning bridge 10 of staple 5 in channel 60 of staple mount 50.Note that in this position, legs 15 of staple 5 are in their unbiased,pointed inward position. FIG. 7 shows staple 5 after handles 45 ofdelivery device 30 have been moved together, so that staple mount 50 isin its open (i.e., staple-straining) position. This is done by movinghandles 45 of delivery device 30 together, thereby forcingstaple-stretching linkages 65 of staple mount 50 apart, and causingbridge 10 of staple 5 to be stretched and causing legs 15 of staple 5 tobe positioned substantially perpendicular to the longitudinal axis ofbridge 10.

Note that with delivery device 30, the delivery device is constructed sothat upon squeezing handles 45, the legs of the staple are first bent toperpendicular and then, when the legs of the staple are substantiallyperpendicular, the bridge of the staple is elongated.

Note that staple 5 is configured so that the force that is generated asstaple 5 reconfigures (i.e., as bridge 10 foreshortens and legs 15 bendinward) is less than the “tear through” force of the bone receiving legs15, i.e., staple 5 is specifically engineered so as to not “tearthrough” the bone tissue when attempting to reconfigure. Delivery device30 preferably includes the aforementioned locking feature 55 whichenables the surgeon to control the extent to which the staple isstrained (e.g., to bend only the legs of the staple, or to both bend thelegs of the staple and strain the bridge of the staple, and to controlthe extent to which the bridge is stretched), thereby allowing thesurgeon to tailor the compressive forces and recoverable strain imposedon the anatomy, depending on bone quality. The compressive forces ofstaple 5 can be controlled by modulating the material properties of thestaple and/or the geometry of the staple.

The percentage of cold work in the shape memory material forming staple5 affects the compressive force generated by the reconfiguring staple.As the percentage of cold work increases, the compression forcedeclines. A staple should, preferably, have between about 15% and 55%cold work to control the recovery force of the staple; however, otherdegrees of cold work may be used, and/or the material may not be coldworked at all.

Another material property that affects the staple's compression force isthe temperature differential between the body that the staple will beimplanted into (assumed to be 37° C., which is the temperature of ahuman body) and the austenite finish temperature of the shape memorymaterial forming staple 5. A smaller temperature differential betweenthe two will result in the staple generating a smaller compressive load;conversely, a larger temperature differential between the two willresult in the staple generating a larger compressive load. The shapememory material that the staple is made out of should, preferably, havean austenite finish temperature of greater than about −10° C., resultingin a temperature differential of about 47° C. when the staple isimplanted (assuming that the staple is implanted in a human body).

Staple geometry also affects the compression forces generated. Thecross-sectional area of bridge 10, and the cross-sectional area of legs15, affects the compression forces generated by the reconfiguringstaple. As the cross-sectional areas increase, so do the compressionforces that the reconfiguring staple will generate.

The staple legs are critical for transmitting the compression force tothe bone without “tearing through” the bone. The height, width, andlength of the staple legs, and the geometry of the staple legs, are allsignificant relative to the staple's ability to not “tear through” thebone. Staple legs with greater surface area are better able todistribute the compression force and thus not “tear through” the bone.

FIG. 8 shows how staple 5 may be used to reduce a fracture and generateand maintain greater, and more uniform, compression between bonefragments 80 and 85 to aid in fracture healing.

More particularly, the fracture 90 to be fused is first re-approximatedand reduced. A drill guide (not shown) of the sort well known in the artis used to drill two holes 95 the correct distance apart to accommodatethe legs 15 of the strained staple 5. Staple 5 is loaded onto deliverydevice 30, and delivery device 30 is used to stretch bridge 10 andstraighten legs 15 of staple 5 (i.e., by squeezing together handles 45).While still on delivery device 30, legs 15 of staple 5 are placed intothe pre-drilled holes 95. Staple 5 is then released from delivery device30, which allows the stretched bridge 10 of staple 5 to foreshorten soas to apply compression to the fracture line, and which allows thestrained legs 15 of staple 5 to “kick in” and thereby apply additionalinward pressure across the fracture line 90. Thus, staple 5 applies moreuniform compression across the fracture site, generating compressionacross both the cortical and intramedullary surfaces, using thecompressive forces generated by the foreshortening bridge 10 of thestrained staple 5 and using the compressive forces generated by inwardlybending legs 15 of the strained staple 5.

Significantly, when bridge 10 and legs 15 of staple 5 generate acompressive force, both the cortical regions of the bone fragments andthe cancellous regions of the bone fragments are pulled together. Thisprovides a superior balance of compression across different regions ofthe bone.

It should also be appreciated that, if desired, staple 5 can be used toattach soft tissue to bone (e.g., to attach a rotator cuff to bone).

It should be appreciated that delivery device 30 may not always seat thestaple with the bridge of the staple seated directly against thecortical surface of the bone (i.e., the bridge of the staple may sitslightly above the cortical surface of the bone). Therefore, a tamp ofthe sort well known in the art may be used to fully seat the staplebridge against the cortical surface of the bone.

In some circumstances it can be desirable to modify delivery device 30so as to ensure that legs 15 do not be bent past 90 degrees (relative tothe longitudinal axis of bridge 10) when staple 5 is strained. Moreparticularly, in some constructions, staple 5 can require more force tostretch bridge 10 than to bend legs 15. In this circumstance, there isthe possibility that legs 15 will be bent to 90 degrees (relative to thelongitudinal axis of bridge 10) and then, as bridge 10 is stretched,legs 15 may be bent past 90 degrees (relative to the longitudinal axisof bridge 10). Therefore, it can be desirable to provide means forpreventing legs 15 from being bent past 90 degrees (relative to thelongitudinal axis of bridge 10). To this end, and looking now at FIGS.8A, 8B and 8C, delivery device 30 may be constructed so that itsstaple-straining linkages 65 are each formed with an outboard constraint97, whereby to prevent legs 15 from being bent past 90 degrees (relativeto the longitudinal axis of bridge 10) when the staple is strained.

In one preferred form of the invention, staple 5 and delivery device 30are provided in the form of a sterilized kit. The kit may includeadditional instruments to aid in the implantation of the staple (e.g.,k-wire, drill bit, staple size guide, tamp, etc.).

In the foregoing discussion, staple 5 is strained so that, upondeployment in the bone, it will provide compression across a fractureline. However, it should also be appreciated that, if desired, staple 5can be configured to provide a distraction force to a bone. In thissituation, staple 5 can be configured and strained so that bridge 10 canbe compressed, and/or legs 15 can be bent outward, such that when staple5 is deployed in bone, the reconfiguring staple can apply a distractionforce to the bone, whereby to cause the bone to grow and therebyelongate.

Novel Staple Comprising Malleable Bridge with Two Elastic Legs

As discussed above, staple 5 is manufactured from a shape memorymaterial (e.g., a material capable of exhibiting superelasticity and/ora temperature-induced shape change). The shape memory material may be ametal alloy (e.g., Nitinol) or a polymer (e.g, appropriately processedPEEK). In this respect it should be appreciated that staple 5 can bemanufactured out of a single piece of shape memory material (i.e., so asto create an integral, monolithic structure), and the different regionsof the staple worked differently, in a metallurgical sense, so thatdifferent regions of the staple have different mechanical properties andexhibit different mechanical characteristics, even as they form asingle, integral, monolithic structure.

In one form of the invention, and as discussed above, staple 5 can bemanufactured so that bridge 10 is elastic, legs 15 are elastic, andcurved hinge regions 20 are elastic, in which case bridge 10 can beelastically deformed, and legs 15 can be elastically deformed, so thatboth bridge 10 and legs 15 provide compression to the fracture siteafter implantation. In this form of the invention, bridge 10 and legs 15may be worked, metallurgically, so that they have the same or differentmechanical properties.

However, in another form of the invention, staple 5 can be manufacturedso that bridge 10 is malleable and non-superelastic (e.g., fullyannealed Nitinol, or martensitic Nitinol with an austenite starttemperature greater than body temperature), and legs 15 and hingeregions 20 are superelastic (e.g., austenite but capable of formingstress-induced martensite). This allows the malleable bridge 10 ofstaple 5 to be inelastically bent (i.e., to take a set) to accommodate aparticular geometry of the cortical anatomy, while still allowing thesuperelastic legs 15 of the staple to generate compression. By way ofexample but not limitation, many bones exhibit an hour-glass surfaceprofile; moreover, certain orthopedic indications (e.g., an AkinOsteotomy) often results in a cortical surface that is concave when thebones are re-approximated. In these situations, a staple with a straightbridge will not sit flush on the bone surface, which can lead to patientdiscomfort. In this respect it should also be appreciated that wherebridge 10 is malleable and legs 15 are superelastic, legs 15 of staple 5may be manufactured at a more acute angle (FIG. 10) so as to allow foradequate fracture compression and reduction in the event that bridge 10must be bent downward (e.g., deformed to a concave position) to meet theanatomical structure of the cortical bone.

See FIG. 9, which shows a monolithic staple 5 where bridge 10 ismalleable and legs 15 are superelastic, and where staple 5 is shown inits unbent and unstrained condition; and FIG. 10, where bridge 10 ofstaple 5 has been bent to give it an altered configuration. Note thatstaple 5 shown in FIGS. 9 and 10 is preferably formed out of a singlepiece of shape memory material, whereby to form a single, integral,monolithic structure, with the single piece of shape memory materialhaving different regions of the staple worked differently, in ametallurgical sense, so that different regions of the staple havedifferent mechanical properties and exhibit different mechanicalcharacteristics, i.e., bridge 10 is malleable and legs 15 aresuperelastic.

It may be desirable for staple 5 to start with a bridge that is convex,e.g., such as the staple 5 shown in FIG. 10A. This will allow the bridgeof the implanted staple to sit flush with the cortical bone surface ifthe bone surface is largely planar. More particularly, if the bridge ofstaple 5 were to be linear, and the legs strained and the stapleinserted into a prepared fracture site where the cortical surface islargely planar, the resulting implanted staple could have two small“humps” at the outer ends of the bridge, i.e., at the bridge-hingeinterface. Starting with a convex-shaped bridge (i.e., such as is shownin FIG. 10A) largely eliminates these “humps”.

Thus, in a second form of the invention, staple 5 is formed out of asingle piece of shape memory material (i.e., so as to form a single,integral, monolithic structure), with the shape memory material beingworked so that bridge 10 is malleable (e.g., fully annealed Nitinol, ormartensitic Nitinol with an austenite start temperature greater thanbody temperature) and legs 15 are superelastic (e.g., austenite butcapable of forming stress-induced martensite), such that bridge 10 ofstaple 5 may be bent to contour to the surface of the bone while thecompressive force generated by the superelastic legs 15 of the stapleare used to help fuse the bone.

A bending device can be used to bend bridge 10 of staple 5 prior toimplantation of the staple. An exemplary bending device 100 is shown inFIG. 11. Bending device 100 is essentially a modified plier assembly.Staple 5 is placed into the bending fixture 105 of bending device 100;compressing the handles 110 causes bridge 10 of staple 5 to be bent tobetter meet the shape of the cortical bone surface.

More particularly, FIG. 12 shows a close-up of bending fixture 105 ofbending device 100. Two pins 115 are used to locate the staple, and athird pin 120 is used to bend the bridge of the staple when the handles110 of bending device 100 are compressed. A channel 125 in bendingfixture 105 both directs the shape of the contour while also serving tolimit the maximum bend imposed on the bridge of the staple.

After the bridge of the staple has been bent to the desired geometry(e.g., the geometry shown in FIG. 10), the legs of the staple can bestrained open (e.g., to the geometry shown in FIG. 13) so as to allowthe bent, strained staple to be inserted into the prepared fracturesite. By way of example but not limitation, and looking now at FIG. 14,the bent staple may be strained using a plier assembly 130 comprising apair of handles 135 and a straining fixture 140. The previously-bentstaple is placed into straining fixture 140, and compressing handles 135causes the staple's legs 15 to be strained opened to parallel.

Plier assembly 130 is also used to insert the staple into the bone afterthe legs of the staple have been strained open to substantiallyparallel.

FIGS. 15 and 16 show the construction and function of straining fixture140 in greater detail. Staple 5 is supported by two internal pins 145and two external pins 150. Compressing handles 135 cause the staple legsto move from an inward-pointing configuration (FIG. 15) to a more open(e.g., parallel) state (FIG. 16). The previously-bent staple, with thelegs now strained to the open state, is then ready for implantationacross the fracture line. When implanted in bone and thereafter releasedfrom plier assembly 130, the strained legs 15 of staple 5 then kickinward, reducing the fracture and generating and maintaining compressionacross the fracture.

FIGS. 17 and 18 show how a staple formed out of a shape memory material,with its bridge being malleable (e.g., fully annealed Nitinol, ormartensitic Nitinol with an austenite start temperature greater thanbody temperature) and its legs being superelastic (e.g., austenite butcapable of forming stress-induced martensite), may be used to reduce afracture 160 between two bone fragments 165, 170 and generate andmaintain compression across the fracture. Significantly, because thebridge of the staple is malleable and the legs of the staple aresuperelastic, the bridge of the staple can be first bent to match thesurface profile of the bone while enabling the superelastic legs of thestaple to be elastically strained to provide the compressive forceacross the fracture.

Looking now at FIGS. 17 and 18, staple 5 is first loaded onto bendingdevice 100 and the bridge of the staple is bent to accommodate thesurface profile of the patient's cortical bone anatomy. The surgeon mayuse fluoroscopy or trial-and-error to bend the bridge of the staple tothe appropriate configuration. With the bridge of the stapleappropriately bent, a drill guide (not shown) is used to drill holes 175into the bone fragments 165, 170 at the appropriate locations on eitherside of the fracture line 160 to accommodate the strained staple legs.Staple 5 is then loaded onto plier assembly 130, and superelastic legs15 are then elastically bent to the open state.

With the bridge of the staple inelastically bent into the appropriateconfiguration and with the legs of the staple elastically strained tosubstantially parallel, the staple can be inserted into the pre-drilledholes 175 in bone fragments 165, 170. The staple is then released fromplier assembly 130 and tamped to sit flush with the cortical surface,with the inelastically bent bridge 10 of the staple more closelymatching the surface contour of the bone. The elastically-strainedsuperelastic legs 15 of the staple applies a compressive force acrossthe fracture.

If desired, where the staple is provided with a malleable bridge, themalleable bridge may be bent, or further bent, after the staple has beendeployed in bone, e.g., to match, or to more closely match, the surfaceprofile of the bone.

In some circumstances the bone may have a convex profile. In thiscircumstance, it may be desirable to set the staple so that its bridgehas a convex configuration. To this end, and looking now at FIG. 19,there is shown a staple 5 which has been inelastically bent to have aconvex bridge 10 and two legs 15.

FIGS. 20 and 21 show another bending device 180 which may be used tobend the bridge of a staple, e.g., the bridge 10 of the staple 5 shownin FIG. 10A. Bending device 180 generally comprises a housing 185supporting a pair of pins 190. Pins 190 receive staple 5 in the mannershown in FIG. 21. Bending device 180 also comprises a screw mechanism195 which selectively advances an element 200 toward pins 190 orretracts element 200 away from pins 190. As a result of thisconstruction, when staple 5 is mounted on pins 190, screw mechanism 195can be used to drive element 200 against bridge 10 of staple 5, wherebyto bend the bridge of the staple.

It should also be appreciated that, if desired, staple 5 can be used toattach soft tissue to bone (e.g., to attach a rotator cuff to bone).

It should be appreciated that delivery device 130 discussed above maynot always seat the staple with the bridge of the staple seated directlyagainst the cortical surface of the bone (i.e., the bridge of the staplemay sit slightly above the cortical surface of the bone). Therefore, atamp of the sort well known in the art may be used to fully seat thestaple bridge against the cortical surface of the bone.

In one preferred form of the invention, staple 5, bending device 100and/or bending device 180, and delivery device (i.e., plier assembly)130 are provided in the form of a sterilized kit. The kit may includeadditional instruments to aid in the implantation of the staple (e.g.,k-wire, drill bit, staple size guide, tamp, etc.).

Test Data

Conventional shape memory staples typically generate between about 20Nand about 120N of compressive force from the staple legs kicking inward.

The novel staple of the present invention having a stretched bridge asdescribed herein generates a compressive load of greater than the 20N to120N generated by other like-sized conventional staples, therebyproviding significantly increased compressive forces without tearingthrough or otherwise damaging the bone. Additionally, the compressiveforce provided by the stretched bridge staple of the present inventionis more uniformly distributed across the fracture line (i.e., across thecortical bone and the cancellous bone).

Modifications of the Preferred Embodiments

It should be understood that many additional changes in the details,materials, steps and arrangements of parts, which have been hereindescribed and illustrated in order to explain the nature of the presentinvention, may be made by those skilled in the art while still remainingwithin the principles and scope of the invention.

What is claimed is:
 1. A method of treating a patient comprising: a)deforming a bridge of a shape memory material staple to conform to ananatomical structure of the patient, wherein a bending device deformsthe bridge by selectively advancing an element against the bridge by ascrew mechanism, and wherein i) the staple comprises an elastic bridgeand two elastic legs, ii) the legs meet the bridge at a curved, elastichinge region, iii) the staple is an integral structure of shape memorymaterial, and iv) the staple is received by a pair of pins on thebending device; and b) implanting the deformed staple into a bone of thepatient, wherein the bridge of the staple is flush with a corticalsurface of the bone.
 2. The method of claim 1, wherein the shape memorymaterial is nitinol.
 3. A method of treating a patient comprising: a)deforming a bridge of a shape memory material staple to conform to thepatient's anatomical structure, wherein the staple is deformed whilemounted to a bending device, and first and second legs of the stapleextend substantially parallel after being deformed by advancing a screwmechanism of the being device to drive an element against the bridge ofthe staple; and b) implanting the deformed staple into a bone of thepatient, wherein the bridge of the staple is flush with a corticalsurface of the bone.
 4. The method of claim 3, wherein the shape memorymaterial is nitinol.
 5. The method of claim 3, wherein the implanting ofthe deformed staple comprises inserting the first and second legs of thedeformed staple into pre-drilled holes in the bone.
 6. The method ofclaim 5, wherein the first and second legs of the deformed staple areimplanted on either side of a fracture line.
 7. The method of claim 3,wherein the implanting of the deformed staple attaches soft tissue tothe bone.